Is there a word or phrase that means both to "re-create" and "improve"? I would like to say "___ our language", meaning to create a new lingua franca from scratch. The word should imply starting over as well as improving over the current state.
Reinvent might be the word you're looking for.
to make as if for the first time something already invented
to make major changes or improvements to (something)
Reconstruct or Modify or Modernize
build or form (something) again after it has been damaged or destroyed
make partial or minor changes to (something), typically so as to improve it or to make it less extreme.
adapt (something) to modern needs or habits, typically by installing modern equipment or adopting modern ideas or methods.
(Definitions from Oxford Languages)